An Overview of the Photocatalytic H2 Evolution by Semiconductor-Based Materials for Nonspecialists

The solar-to-chemical energy conversion is promising to tackle sustainability challenges toward a global future. The production of H2 from sunlight represents an attractive alternative to the use of carboniferous fossil fuels to meet our energy demands. In this context, the water splitting reaction photocatalyzed by semiconductors that can be excited under visible or near-infrared light excitation represents an attractive route to the clean generation of H2. In this review, we present an overview of the most important concepts behind the H2 generation, from water splitting, promoted by semiconductor-based systems for readers that were recently introduced to the water splitting topic. Then, we present the main classes of photocatalysts based on semiconductors. For each class of semiconductors, we focused on the examples that lead to the highest activities towards the H2 production and discuss the operation principles, advantages, performances, limitations, and challenges. We cover metal oxides, sulfides, and nitrides. We also discuss strategies in which these materials are combined, including hybridization with metal nanoparticles, other semiconductors, and carbon dots, to achieve improved performances and circumvent the limitations of the individual counterparts.